This lesson is a review and summary of the various types of past tense structures in the Korean language. There is only one basic past tense structure, the suffix -았/었/였, but by using other structures, you can add more specific meanings to your sentences. 1. Basic Past Tense with "-았/었/였" (Level 1 Lesson 17)Verb stem + -았/었/였 + -어요Ex) 사다 = to buy → 사 + -았어요 = 샀어요 = I (or someone else) bought it. 주다 = to give→ 주 + -었어요 = 줬어요 = I gave it (to someone). 2. -았/었/였었어요 To emphasize that one “had” done something in the past or before another action/state, some people add the suffix one more time, making it -았/었/였었어요 instead -았/었/였어요.Ex) 보다 = to see, to watch→ 보 + -았어요 = 봤어요 = I saw.→ 보 + -았 + 었어요 = 봤었어요 = I saw it a long time ago. I had seen it before.3. -고는 했어요To talk about something that you used to do regularly or habitually, you can use the ending “-고는 했어요.” When you use -고는 했어요 after a verb, it implies that you don’t do it any longer. Ex)보다 = to watch→ 보 + -고는 했어요 = 보고는 했어요 = I used to watch.밤 늦게까지 TV를 보고는 했어요.= I used to watch TV until late at night.가끔 친구들을 만나고는 했어요.= I used to meet my friends from time to time.4. -ㄴ/은 (Level 4 Lesson 26)-ㄴ/은 is the conjugation you can use after a verb stem to modify a noun. -ㄴ/은 needs to be followed by the noun that the verb modifies either as the object or the subject. Ex)마시다 = to drink마시 + -ㄴ = 마신 = that I drank어제 마신 커피 = the coffee that I drank yesterday아까 이야기한 책 = the book I talked about earlier이 책을 쓴 사람 = the person who wrote the book5. -던 (Level 8 Lesson 4)-던 is also used after a verb to modify a noun. -ㄴ/은 is the basic verb ending for modifying nouns, but if you use -던, you can add the nuance of “used to” or “was doing but didn’t finish”. Ex)마시다 = to drink→ 마신 = (something) that I drank→ 마시던 = (something) that I was drinking, (something) that I used to drink그거 제가 마시던 커피예요. = That’s the coffee I was drinking (but didn’t finish). 어렸을 때 제가 좋아했던 만화책이에요. = It’s a comic book that I used to like when I was a kid.6. -(으)ㄹ 뻔 했어요 (Level 5 Lesson 1)When you say -(으)ㄹ 뻔 했어요 after a verb stem, it means that something “almost happened” or that you “almost did” something. Ex)잊다 = to forget→ 잊 + -(으)ㄹ 뻔 했어요 = 잊을 뻔 했어요 = I almost forgot.넘어지다 = to fall down (on the ground)→ 넘어질 뻔 했어요. = I almost fell down.너무 놀라서 소리를 지를 뻔 했어요.= I was so surprised that I almost screamed.너무 무거워서 떨어뜨릴 뻔 했어요.= It was so heavy that I almost dropped it.7. -아/어/여 봤어요 (Level 4 Lesson 12)-아/어/여 보다 means “to try doing something” or “to give something a try”. By using this in the past tense, you can say “I’ve tried doing + something + before” or “I have done + something + before” in Korean.Ex)듣다 = to listen→ 듣 + -어 보다 → 들어 보다 (irregular conjugation)→ 이 노래 들어 봤어요? = Have you heard this song (before)?이거 읽어 봤어요? = Have you read this? / Have you tried reading this? 8. -(으)ㄴ 적 있어요-(으)ㄴ 적 있어요 is used after verb stems to mean “I have done + something + before”, to talk about one’s experience. You can also use -아/어/여 본 적 있다 to mean the same thing, using the -아/어/여 보다 structure. Ex) 배우다 = to learn→ 배우 + ㄴ 적 있어요 = 배운 적 있어요 = I have learned it before. I have the experience of learning it. → 중국어 배운 적 있어요? = Have you learned Chinese before?→ 중국어 배워 본 적 있어요? = Have you tried learning Chinese before?여기는 와 본 적 없어요. = I haven’t been here before.